Rate of climb indicator



4 Sheets-Sheet l Jam 3f 1939A A. E. slDwELL RATE 0F CLIMB INDICATOR Filed March 6, 19:57/

Syvum Jan. 3, V1939. f A. E. slDwELl.

RATEv OF CLIMB INDICATOR Filled March- 6, 1937 4 Sheets-Sheet 2 'n Agfedgmea.

Jan. 3, 1939. A. E. slDwELL.

RATE 0F CLIMB INDICATOR Filed March s. 1937 4 sheetsshea s Alfred E. ,Sida/6a.

Jan. 3, 1939.

A. E. slDwELL 2,142,338 RATE oF cpm INDICATOR A Filed March 6, 1937 4 Sheets-Sheet 4 Iwo" f A fred E, sida/eu of change of altitude.

Parental .1.11.3,1939- Aurea E. siawu, xcw Gardens, N. Y., mim `to Bendix Aviation Corporation, -South Bend Ind., a corporation of Delaware g p Application March 6, 1937, Serial YNo. 129,504 21 Claims. (Cl. 264-1?.

The present invention relates to pressure rey ponsive indicating instruments andmore particularly to pressure responsive instruments such as aircraft rate of climb indicators, vifor example, wherein a diierential pressure is utilized toactuate `an indicating element to indicate the rate The invention is embodied in an aircraft fate of climb indicator wherein a diierential'pressure is established due to change in altitude and wherein means are provided to equalize said pressure when the altitude ceases tol change.

More specifically,` the rate oi climb indicator embodying the inventionis provided with novel means for regulating the equalization in order to provide compensation for certain conditions. Rate of climb indicators ofthe prior art have been provided with means for equalization of the differential pressure such, for example, as a cap-l llaryk tube or restricted passage but no means were provided whereby inaccuracies due lto .changes in certain conditions of the atmosphere could be compensated, as i'or example, due to changes in temperature or barometric pressure or both.

Upon an increase in temperature above the normal temperature at which the rate of climb indicator is calibrated the air from the inside of the pressure responsive device encountersv freely through the capillary passage, therebyl `maintaining the differential pressure for a shorter period of time than at the normal temperature,

thusgiving anindica'tion of too low a rate of climb.

Upon an increase 'in altitude above sea level the barometric pressure decreases4 and the air becomes raried. This raried air has greater viscosity and hence encounters greater dimculty in flowing through the capillary or restricted passage and, therefore, the device vgives an indication of too high a rate of climb;

Accordingly, one of the objects of the presen invention is to provide, in an instrument of the class described, novel means whereby the foregoing undesirable characteristics are eliminated.

. Another object is to provide a novel rate of climb indicator in which the errors due to changes in certain conditions in the atmosphere, such as temperature and pressure changes due to changes kin altitude are compensated.

A further object is to provide a novel rate ofclimb indicator comprising means establishing a pressure vdifferential proportional tothe rate of climb, and temperature controlled means governing the equalization of.- said vcii'erentlal whereby errorsdue to temperature changes. are

l eliminated.

A' still 4further object is to provide in a novel rate of climb indicator including a pressure responsive element, a plurality of capillary means regulating the flow of air from said element and means responsive to a change in condition o! the atmospherefor regulating the arrangement oi said capillaries.

Other and further 'objects and advantages. of the invention will appear more fully hereinafter from a consideration of the detailed description which follows, taken together with-the accompanying drawings wherein is illustrated one eml bodiment of the invention. It is to be expressly understood,however, that the drawings are for the purposesof illustration only and are not de- Fig. 3 is a plan view of the instrument proper of Fig. 1 with the casing removed;

Fig. 4 is a cross-section showing in ldetail the construction of the reservoir and bellows;

' Fig. 5 is a section illustrating the structure of the capillary tubing and temperature compensation device; f

Fig. 6 is an end view of the device shown inA Fig. e

Fig. '7 is aplan view of the device shown in Fig. 5, and i Fig. 8 is a lsection as in Fig. 5 wherein the temperature responsive device is replaced by' a pressure responsive device. Y

Referring to the drawings and more particularly to Fig. 1, the instrument embodying the present invention, as shown, comprises a casing s in which is mounted the operating mechanism. Said mechanism is mounted on a frame of any suitable type which, in. the pres'entembodiment,"

comprises a rear frame member or plate Il and a face plate II, said plates'being held in spacedrelation by spacers I2 and screws Il. Mounted in the frame thus constituted, is a .pressure responsive ,expansible element or chami ber. I4 adapted to operate an indicating element when a pressure differential is established between vthe pressures, inside and outside'of saidv chamber I4. This may be accomplishedJor example, by providing communication between the atmosphere and the inside of the casing I. The

pressure ot the atmosphere is, therefore, exerted.

on the outside of the pressure chamber I4 while the inside of said chamber is connected to the inside of thecasing and, therefore, to said atthe end I1 of the flexible ann I5 ls bent at an l face plate I I.

angle to said arm and engages the cone-shaped end vI8 of a set screw Il thatis threaded in a bracket 20 mounted on or formed integral with means of a central boss 2| that extends through the ilexible arm I and is secured theretoby means of lock washer 22 and a nut 23, said boss 'being hollow and connected to a tube 24 held in position by tube clamp 2) and in communication with the interior ofthe casing by means of 26, a continuation of tube 24, and the interior of coupling 21 which is connected to the inside of the casing through a capillary assembly and 1totthe reservoir as will be set out more in detail a er.

I'n order to actuate the indicating element or pointer oi' the instrument, suitable connections are provided between the pressure responsive element and the pointer. 'Ihese connections comprise a short post 2l connected to the center of the pressure element I4 onthe side thereof opposite to boss 2| and pivotallyconnected at 2i to one end of link l0. 'lhe other end of link 34 (see Fig. 3) is. pivotally connected at Ii to slott'ed rocker arm 32 on rockshaft Il.. Rockshaft 3l is rotatably mounted in adJustable bearings 34 carried-by a .U-bracket l! secured to plate I0 by screws 36. Mounted on or formed integral with said rockshaft 3l is an arm 31 carrying counterweight 11a adjustably mounted thereon by screw 31h. Movements of element I4 are transferred to said arm I1 by means of the linkages set out above.

In order to limit the movement of ,element I4, post 28 mounted thereon is arranged to be engaged bythe ngers of fork 34 (see Fig. 1)

-whereby the element I4 will abut fork Il after n limited movement in one direction while pin Il secured to the post 2l abuts fork Il upon `limitedomovement of element I4 inthe oppodte direction. Said fork may be so assembledas tobe adjustable longitudinally of post 28 as by mounting it on a rod 44 adjustably connected to-one of the spacers l2 by hollow post 44a and screw IIn order to further transmit the motion of the element I4 by means of its movement vof arm 31 there is mountedon face plate II4 by means 'of spacers4l and screws 42 a V-shaped plate 43. Rotatably mounted in plate 42 is spindle.44. A rod passes through spindle 44 and extends beneath the arm I1 (see Fig. 3)v wh/ereby it can be rotatedlin one direction by said s,14a,sss

Element I4 may be supported by arm l1. Connected to said spindle 44 is a hair spring 4I which rotates the spindle 44 to always move rod 45 against arm l1. In this manner the expansion and contraction of pressure element I4 is converted intorotation of spindle 44 in one direction or the other. counterweighted at 41a carried on said spindle Gear sector 41,

44mesheswithapinion4lcarriedonasecondspindle 4l rotatably mounted in plate 44 (directly below 4l in Fig. l). Said spindle 4I extends through plate II and carries at its outer end a pointer II moving over scale lid.

' The mechanism above. described is mounted in the casing) which may be of any suitable 'material such as Bakeli", the face plate Il being seated against shoulder l2 and held thereagainst by split ring 53 which engages the underside `of a shoulder 54 formed in the casing. The

front end of the casing is closed by means oi cover glass 55 held in place by split ring Il on one side and split facing ring' i1von'the other.

The coupling member 21 is provided with a flange 21a fastened to an insert21b moulded in casing 9. Connected to said insert is a conduit '80 leading to the thermally -insulated expan sion chamber GI.. Flange Il encircling opening from the capillary and thereby reduces the preis-v sure in' element I4 too quickly thereby producing an under-reading or indication by pointer II. Upon an-increase in altitude, the-air escapes less readily from the capillary and, therefore, the pressure inside of I4 reduces too slowly thereby giving an over-reading or indication by pointer 5I.

Fig. 4 illustrates in detail the device used A$0!" altitude compensation which may be of the type disclosed and claimed in co-pending application of Paul W. Koch, Serial No. 119,045, illed January 4, 1937, wherein. bellows arev inserted within the reservoir so that the errors due to changes in altitude are eliminated. l

Referring to Fig. 4, there is provided `a conduit leading from coupling member 21 and oonnected to bushing Cla'passing. through plate 4I riveted to the cap IIa of athermally insulated reservoir 6I. ,Bushing a is connected to a conduit 64 which passes through the base 4I and into the reservoir 6I' which, in the present in- '54a 'in casing Iy is fastened to said 'casingby l `screws I9 andforms the connection means for stance,.comprises the vacuum bottle or heat insulated device I1 centered in a shell IIb by spring Sic (see Fig. 1).` Fastened to said base 4I by the rivet bolt connections 64 and nuts 89 isa base 1l` pands to thereby cut down the elective volum of air in the reservoir.

Means are now provided whereby the errors due to temperature changes and pressure changes Vdue to altitude changes may be connected in series, but under certain conditions one of them lmay be by-passed, whereby the movement of air from element i4 is regulated.'

and the errors due to temperature changes or 'altitude changes are thereby eliminated.

sembly 62 embodying the present invention. They Inrigs. 5 through 7 are shown the details of the combined capillary structure and valve asvalve assembly comprises a base 12 which is fas- ,tened in position by means of threaded sleeve 12a (see Fig. 1) which cooperates with threads on base 12. Head 12b on the threaded sleeve abuts the inside of the coupling 21 to pull base 12 tightly against sealing material 12e.l Sleeve 12a has openings 12d therein leading from coupling 21 to chamber 13 in base 12 (see Fig.1).

Leading from chamber 13 by brazed connectionl .14 (see Fig. 7) is capillary tube 15 (see Fig. 5)

coiled into form 15a and leading to chamber, .16 of the valve structure. Screwed into said chamber 16 is iitting," capped by a screw tting 18 which provides one guide 18 for the rod 80 of a valve 82 cooperating with a valve seat 8| either of which may be tapered', leading to opening 183 and valve ports84. Fitting 11 is provided with guide 8515er the other end of rod 8|l. Spring 86 :normally urges the valve 8i away from the valve seat 82 while a temperature-actuated bi-metallic strip 81 tends to close the valve against the force of spring 86 by pressingagainst rod 80. The

.valve may be designed either to be completely opened or' completely closed or else partially closed to different degrees or completely-closed with varying degrees of opening depending upon Iaccording to the temperature.

,l The thermo-responsivev element 81 is mounted on"=.abase 88 by means of sub-base 8l and ,held thereon by screws 86, 8|, the -latterco-a'ctins with screw 92 to hold the-sub-base on base 88.

Base 88 is. held on base 12 by suitable meansl such as a screw 63. Mounted on base 88 'is set screw 94 whereby the setting o! temperature actuatedelement 81 may be adjusted.

Leading from chamber 1l is a second capillary tube 85 formed into coil 85a andexhausting at 88,

into the interior of casing 8..

Valve 82 serves to controlthe tlow of air from 'the diaphragmv M .and `reeel-voir n tru-ouah capillary tube 16 and valve chamber 161er capillary tubes 15 and l! into casing l. When valve 82 is completely open, the capillary tube 85 is and reservoir 6i must pass through both capillary tubes 15 and I6 before it can escape into the cas- Ling 9 to equalize the pressures inside and outside ofthe diaphragm i4. The strip I1 is so arranged that for the lowest temperature below normal it i iscaused to flex to itslimit to the left (as Aviev'vet'l` in-` Fig. 5) to completely or partly close the valve greater extent than when the valve is completely 1 open andthe air ilows through capillary Il only.

Thus, .the indication of pointer ll, which wouldv otherwise be low at low temperatures, is increased to the correct reading. On the other hand, at

- the extreme hightemperature above normal.' the strip is liiexed to its limit to the right las viewed in Fig. 5) so that the valve 82 is completelyopen and the air iiows through capillary 15 only. For

is calibrated, and for temperatures between normal and the extreme high and low temperatures, the valve 82 is partially open, and more or less according to the prevailing temperature, so that l after owingthrough capillary 16, part of the air may ilow through capillary tube 86 and part through the valve 82. Thus, the amount vof retardation oilered by the capillaries depends upon the temperature and in this manner` the instruthe normal temperature at which the instrument' ment is made to read correctly for all tempera# tures from the highest Ato the lowest.`

The operation of the device is as followsz At ground level air at normal (sea level) atmos- 'pheric pressure enters theinterior of'casing 8 and iiows either through openings 91, uncovered -valve seat 82, ports 84 to chamber 16 and theny past clamp 25, to tube 24 leading to the inside of pressure chamber I4. Wherigfthe'device remains at the same altitude for an appreciable length of :time the pressure inside pressure element I4 and on the outside thereof become equal. The

pointer is then adjusted to zero' by means of knob,

|00 (see Fig. l) which turns pinion Illl to revolve l gear iil2 to rotate set screwl I8 to adjust cone I8` the amount of exure oi the bi-metallic strip 81 and arm I1 so that pointer 5I indicates zero.

Upon anl increase in altitude the pressure within casing 9 assumes the pressure at the new altitude. 'I'his j pressure. is not `immediately 'transferred to the inside of element I4', conselquently said elementu i4@ expands and moves pointer 5I.

hence, the indication of pointer 5I is proportional to the rate of. rise. The pressure insideof element I4 escapes by means of tubing 24, 26, element 21` and capillary 15 to the chamber 16. If the temperature of the airis at the extreme limit below that at which element 81 is adjusted for normal temperature, this element presses against rod,l to hold valve 8l either to close oi` or compietely seal 82and the air from chamber 16is forced to passthrough capillary as well as capillary 15 and escapes at .38. This additional passage through capillary 85, as explained'hereinbeiore, compensates for the tendency of the cooler vair to ilow more freely atthe lowertemperatures. Hence,v the air escapes irom the inside o! pressure velement I4 and reservoir 6l at the desired rate `and 'the under `indication of pointer 6I is avoidedflf the temperaturel is atthe extreme limit above the normal setting.v for element 81the pressure on rod 80 is decreased or removed and air is-aliowed to escape from chamber 16 by ports 84, chamber, uncovered valve As air is always lescaping from |4-` during the rise, the expansion of element vi4 and,

seat 82 and openings 81, thereby bypassing capillary 3|. As air flows less freelythrough the capillaries au; higherV temperatures this Vaow .isv

'increased' by by-passing capillary 83 to thereby compensate-for the 'over-,reading of-pointerii at an incredse. in ltemperature@ For temperatures partially open todiierent degrees so that the air -ilows partially through capillary '93 'and partially through the valve. l f,

between'thewhighest and lowest, the valve 821s" the valve 8l, B2 upon a decrease in pressure.`

Means operated by other conditions of the atmosphere as, for instance, by changes in pressure due to changes in altitude may be used to operate the valve 8|, 82. In such a. case a decrease in pressure will open thevalve to partially 4or completely vby-pass the second capillary.

Such a construction is shown in Fig. 8 which illustrates a device as in Fig. 5 with the exception that the bi-metal element 81 of Fig. 5 is replaced by aneroid element 81a and arm 81h which open The operation is otherwise as described in connection with the device of Fig. 5.

There is thus provided a rate of climb indicator without departing from the scope of the invention. Reference, therefore, is to be had to the.

appended claims for a definition of the limits of the invention.

.What is claimed is: 1. In an instrument of the class described having a pressure responsive element, means whereby th'e atmosphere inside and outside said element is'in communication comprising a chamber, capillary means leading from said chamber to the atmosphere outside said element, capillary means leading from said chamber to the atmosphere inside said element, `said chamber having an opening also communicating withv one of said atmospheres, a valve for controlling said opening, and atmospheric temperature responsive 40 means controllingthe opening of said valve.

2. In combination, an expansible diaphragm having a yieldingwall subject to atmospheric pressure on one sidethereof. a vplurality of elementsfor retarding the rate at which pressure on the other kside of said yielding wall tends to become equal to a changing atmospheric pressure,

indicating means actuated by said yielding waliin accordance with the rate of change of altitude, valve means for byfpassing one of said retarding elements, and temperature responsive. means for operating said valve means. A Y

3. Inv combination, an expansible diaphragm having a yielding wall subject to a changingatmosphe'ric pressure on` one side thereof, a plurality of capillary elements for separately retarding the rate at which pressure on the other side of 4said yielding wall tends to become equal to said changing pressure, indicating means ,actuated bysaid yielding wall in accordance with the rate of change of atmospheric pressure, and means includi means responsive to changes in a condition of the atmosphere for by-passing one of said capillary elements, said condition ofthe atmosphere being one of the group consisting of pressure of the atmosphere and temperature of the atmosphere. f

4. In combination, a chamber, ygas within and outside of said chamber, a plurality of flow restricting elements connected to said chamber, and means including means responsive to changes in thetemperature of the lgas for by-passing cervtain of said restricting elements.

5. In an instrument of theclass described, a plurality of capillary means, and vmeans including temperature responsive means for bycertain of said capillary means.

6. Equalizing means comprising an enclosure, capillary means leading fromy said enclosure to a source of atmospheric pressure, means leading from said enclosure to a different source of pressure, an opening in said enclosure, means controlling said opening. and means responsive to a change in condition of the atmosphere for actuating said last-named means to regulate said opening to control the 'by-passing oi' said capillary means, said condition of the atmosphere being one of the group consisting of pressure of the atmosphere and temperature of the atmosphere.

'1. In an instrument of the class described, having'a/pressu chamber, means whereby the atmosphere inside and outside said chamber is in communication comprising a plurality of capillary` elements serially arranged in the path of travel of said atmosphere, and means including means responsive to changes in the temperature nof the atmosphere-for by-passing one of said elements.

8. In an instrument ha'ving a pressure element, means whereby the atmosphere inside and outside said element is in communication comprising a chamber, a capillary means interposed between said chamber and said inside atmosphere, capillary meansinterposed between said chamber and said outside atmosphere, an opening in said chamber directly communicating with one of said atmospheres, valve means controlling said opening, and means responsive to changes in temperature-of the atmosphere for actuating said valve means to control said opening.

9. Equalizing means comprising a hollow body,

a capillary element leading from said body to a4 source of pressure, a second capillary leading from said body to a different pressure, an opening in said body, a valve controllng said opening, and temperature responsive means for actuating said valve whereby one'of said elements is incremen- V tally by-passed.

10. In an instrument of the class described, a

casing, an opening in .said casing leading tothe -having a yielding wallr subject to atmospheric pressure on one side thereof, a plurality of elements for separately retarding the rate at lwhich pressure on the Iother 'side of said yielding wall tends to become equal to a changing atmospheric pressure, and means responsive to changes in a condition of the atmosphere for modifying the retarding action of one of said retarding elements; said condition of the atmosphere being one of the group consisting of pressure of the atmosphere and temperature of the atmosphere.

12.` In combination,v an expansible diaphragm vhaving a yieldingwall subject to atmospheric pressure on one s'ide thereof, a plurality of elements for separately retarding the rate at which pressure on the other side of said yielding wall tends to become equal to a changing" atmospheric pressure.. means responsive to changes in a condition of the atmosphere for modifying the retarding action of one of said retarding elements, said condition of the atmosphere being one of the group consisting of pressure of the .atmos' phere and temperature of the atmosphere, and indicating means actuated by said yielding wall in accordance with the rate of change of altitude.

13. In a device of the character described, a

flow controlling assembly comprising a plurality of capillary elements, and control means responsive to temperature changes for rendering certain 'of said elements ineffective.

14. In a device of the character described, a

iiow controlling assembly comprising a plurality' of capillary elements, and means including means responsive to a change in a condition of the atmeans responsive to al change in a condition of the atmosphere for by-passing'certain of said capillary means. said condition of the atmosphere being one of the group consisting of pressure of the atmosphere and temperature of' the atmosphere.

16. In combination, an expansible' diaphragm device having a yielding wall subject to atmospheric pressure on one side thereof, a plurality of elements for retarding the rate at which pressure on the other side oi said yielding wall tendsto become equal -to a changing atmospheric pressure, and means responsive to changes in a condition of the atmosphere for modifying the retarding action of one of said retarding elements, said condition of the atmosphere being one of the group consisting of pressure of the atmospher and temperature of the atmosphere.

17. In combination, an expansible diaphragm device having a yielding wall subject to atmospheric pressure on one side thereof, avplurality of elements for retarding the rate at which pressure on the other side of said wall tendsto become responsive to changes in a condition of the atmosphere for modifying the retarding action of one of said retarding elements, said condition of the atmospherej being one of the group consisting of pressure of the atmosphere and temperature of the atmosphere, and indicating means actuated by said yielding wall.

18. In a rate of climb .responsive device, the

combination with a chamber enclosing a volume of air, 'and a differentialv pressure responsive' member connected to respond to a diierence in lpressure between said chamber and the atmospheric air. of a plurality of air flow retarding elements connecting said chamber kand the atmosphere, and means responsive to a condition of the atmosphere for controlling the retarding action of at least one f saidretarding elements, said condition of the atmosphere being one oi the group consisting of pressure of the atmosphere .and temperature oi the atmosphere.

19. In a rate of climb responsive device, the

combination with a chamber enclosing a volume of air, and a differential pressure responsive memsure between said chamber and the atmospheric air, of a plurality of airflow retarding elements ber connected to respond to a difference in presvconnecting said chamber and the atmosphere,

and temperature responsive means for controlling the] retarding action of at least one of said retarding elements.

20. In a device of the class described, a plurality of ilow retarding elements at least one oi said elements comprising a capillary and control trol means responsive to a change in a condition of-. the atmosphere for rendering certain of said elements ineiective, said condition of the atmosphere being one of the group consisting Vof pres-v sure ofthe atmosphere and temperature of the atmosphere.

ALFRED E. SIDWELL. 

